Anyone know any ways to block GPS spy devices?

Are there any ways that you know of to block a GPS spying device? Like the type nearly anyone can purchase and put on someone's car to spy on where they go.

I'm not asking so much about the type that transmits a rf signal in real time, because those would be easier to block. Though info on that type would be interesting as well. I'm more concerned with the type that just sit there and keep a log of everywhere you go and then can be later retrieved by whomever put it there and all its contents/records downloaded to their pc for viewing.

It doesn't seem very fair to me that anyone can so easily get their hands on one of these spy devices, but there are no easy ways, that I'm aware of, to block them. I'm surprised they're legal to buy, by the average consumer, but they are. I would think anyone who is concerned about their privacy would be interested in this issue, yet there seems to be little discussion about it anywhere.

Thanks for any tips.

 

Any type of Wave scrambler works!
Go to your local spy shop. Whatever fries Wireless phones and Cellular networks also blanks GPS (locally only since GPS is satellite based)

Any GPS device requires some RF (to satellites in this case) so this is applicable. Also make sure the device you build (Yes build) or purchase emits a weak field as not to disturb other more important GPS based vehicles that may operate near by like ambulances and firetrucks or police cruisers. Many fleet vehicles would suffer technical blackout because of this. so be careful. Another side effect would be your car radio... it wouldn't work unless you know the exact frequency of the device to jam and not overlap...

Here is a nice article on Jammers...
http://electronics.howstuffworks.com/cell-phone-jammer1.htm